From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 3859 invoked by alias); 29 Nov 2012 09:13:57 -0000 Received: (qmail 3849 invoked by uid 22791); 29 Nov 2012 09:13:55 -0000 X-SWARE-Spam-Status: No, hits=-7.8 required=5.0 tests=AWL,BAYES_00,KHOP_RCVD_UNTRUST,KHOP_THREADED,RCVD_IN_DNSWL_HI,RCVD_IN_HOSTKARMA_W,RP_MATCHES_RCVD X-Spam-Check-By: sourceware.org Received: from mga03.intel.com (HELO mga03.intel.com) (143.182.124.21) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 29 Nov 2012 09:13:50 +0000 Received: from azsmga001.ch.intel.com ([10.2.17.19]) by azsmga101.ch.intel.com with ESMTP; 29 Nov 2012 01:13:48 -0800 X-ExtLoop1: 1 Received: from irsmsx103.ger.corp.intel.com ([163.33.3.157]) by azsmga001.ch.intel.com with ESMTP; 29 Nov 2012 01:13:46 -0800 Received: from irsmsx102.ger.corp.intel.com ([169.254.2.95]) by IRSMSX103.ger.corp.intel.com ([169.254.3.74]) with mapi id 14.01.0355.002; Thu, 29 Nov 2012 09:13:45 +0000 From: "Metzger, Markus T" To: Jan Kratochvil , Markus Metzger CC: "gdb-patches@sourceware.org" , "palves@redhat.com" , "tromey@redhat.com" , "kettenis@gnu.org" Subject: RE: [patch v4 00/13] branch tracing support for Atom Date: Thu, 29 Nov 2012 09:13:00 -0000 Message-ID: References: <1354013351-14791-1-git-send-email-markus.t.metzger@intel.com> <20121127131055.GB22431@host2.jankratochvil.net> <20121127143235.GA31270@host2.jankratochvil.net> <20121127153603.GA1899@host2.jankratochvil.net> <20121127162740.GA4512@host2.jankratochvil.net> <20121127175955.GA8901@host2.jankratochvil.net> <11AC197E-8662-45CB-9D99-355786849BD8@gmail.com> <20121128190113.GA20881@host2.jankratochvil.net> In-Reply-To: <20121128190113.GA20881@host2.jankratochvil.net> Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-IsSubscribed: yes Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org X-SW-Source: 2012-11/txt/msg00844.txt.bz2 > -----Original Message----- > From: gdb-patches-owner@sourceware.org [mailto:gdb-patches-owner@sourcewa= re.org] On Behalf Of Jan Kratochvil > Sent: Wednesday, November 28, 2012 8:01 PM > To: Markus Metzger > Cc: Metzger, Markus T; gdb-patches@sourceware.org; palves@redhat.com; tro= mey@redhat.com; kettenis@gnu.org > Subject: Re: [patch v4 00/13] branch tracing support for Atom >=20 > On Tue, 27 Nov 2012 19:56:07 +0100, Markus Metzger wrote: > > I hard-coded one page of trace (or, rather, perf_event) buffer per thre= ad. > > We could make this configurable. I have not done this, yet, since I wan= ted > > to keep the patch series small and simple until I get feedback. >=20 > Sorry for not reading the kernel arch code etc. for it but if the buffer = is so > small - mostly just catching the last jump to NULL, I would find better if > kernel does not have to trap at all and saves just the last 4 or 16 jumps= IIRC > without any performance penalty, is there such an option? We can make the buffer size configurable. I just hard-coded one page inside= gdb. The kernel allows you to request larger buffers. Yes, there is another hardware feature called LBR that contains the same in= formation in a register-based ring buffer. This will give the last few bran= ches. It is currently lacking a kernel interface to access those registers.= If we added such an interface, we could make the trace recording method co= nfigurable and allow the user to choose between small trace without overhea= d or big trace with noticeable overhead. I don't know the exact overhead of= LBR's. I would expect that if there is any overhead it shouldn't be notice= able. > Sure some full buffer recording with virtual backtraces and reverse-* wou= ld be > fine but that is probably out of the scope of this initial patchset. Agreed. Regards, Markus. Intel GmbH Dornacher Strasse 1 85622 Feldkirchen/Muenchen, Deutschland Sitz der Gesellschaft: Feldkirchen bei Muenchen Geschaeftsfuehrer: Peter Gleissner, Christian Lamprechter, Hannes Schwadere= r, Douglas Lusk Registergericht: Muenchen HRB 47456 Ust.-IdNr./VAT Registration No.: DE129385895 Citibank Frankfurt a.M. (BLZ 502 109 00) 600119052